I. Field of the Invention
When light passes through media: water, planar glass lens then air, it gets the max incident angle only around 48.61 degree. This describes why so narrow vision under water is presented to divers mounted with conventional diving mask. Efforts of the invention are related to a device of “wide-angle diving lens” especially refers to offer solutions to conquer the light physics limits. The solutions include molding planar sub-window, inner edge Fresnel prism, and lens profile ends embedded joint or their combinations. This “wide-angle diving lens” is not only increase the light incident angle to broaden the visible field but also reinforce the lens structure solidity.
II. Description of the Prior Art
The most conventional diving mask consists of plastic frame, rubber skirt and tempered glass lens; tempered glass lens generally is planar. Owning to the limits of the light physics, when light passes from high index to low index media, it will cause total reflection if the incident angle is beyond its critical incident angle. The max incident angle is only around 48.61 degree for a conventional diving mask lens. Therefore, the visible range of a diver under water is around 97.22 degree after plus two eyes' visible range. Please refer to FIG. 1, when light (as per route 1) passes within the critical incident angle, it is visible to human eyes; but when the light passes from critical incident angle (as per route 2) it will go along with the lens's surface and cannot be seen by human eyes; when light (as per route 3) passes beyond 48.61 degree critical angle, it will make reflection to form a blind zone.
Please also refer to FIGS. 2A, 2B, which show that the visible range from top and side view of conventional single planar diving lens. Divers should adjust them self several times and are very inconveniently in the water to scan the whole surroundings due to limited visional zone.
Refer to FIG. 3A to 3D, owning to the defects of the conventional lens, several improvements on diving lens was used to enlarge the visible angle. The first category of conventional improvement was to join multiple lenses with plastic frame resin into U-shape, but it always causes vision separate and shift between joints of lenses. The second category is integrally built in an arc lens, and has one dimension curved surface, but it causes faintness in the water. The third category of diving lens combines a front planar lens with an extended curved side lens, which was made by molding and used to increase the light income, but the side lens image quality is not good enough. The last category is a kind of polygonal lens, made by glued lenses, which cut the edge of lenses into a certain angle then glue them together to diminish visional fractions, but it leads to the defect of weak structure. In general case, conventional lens mounted on plastic frame will shape a plastic frame convex at the edge of lens, which will sabotage the incident light and also limit the light incident angle.
In recent years, the lens processing technique progress very fast, and the raw materials of lens become diverse, optical resin (such as PC, Acrylic, etc.) by injection, thermal setting CR39 casting to produce plastic lens appear. The above-mentioned techniques are highly matured, even the press technique of high-precision glass-mold are gradually commercialized. The high-precision glass molding machine and the high-precision glass-mold processing machines are prevalently available in the open market. Accordingly, the present invention makes use of the above-mentioned materials and techniques to manufacture molding integral “wide-angle diving lens.” It not only increases light passes the lens to enlarge visible range but also strengthens the structure. In addition, Fresnel prism arranged on inner edge could be used to modify the light refraction angle to enlarge the visible range and decrease the thickness of lens.